A vast number of applications exist in which it is necessary or desirable to monitor the presence and/or position of one or more components of a composite article during manufacturing. For instance, in a largely automated process for manufacturing disposable absorbent products such as diapers and other incontinence products, certain components (e.g., support layers, absorbent pads, elastic components, fastener components, etc.) must be positioned or aligned with respect to each other and/or other components in order to produce an acceptable product. Accordingly, inspection systems are commonly used to detect the positions of such components during manufacturing. If an inspection system determines that one or more components are out of position and thus do not properly register with other components, the inspection system typically outputs one or more signals indicating that certain articles should be culled and discarded, that the process should be adjusted so as to bring out-of-position components into proper position, that the process should be adjusted so that subsequent components are brought into proper registration with one another, etc.
An exemplary registration inspection system is disclosed in U.S. Pat. No. 5,359,525, the disclosure of which is incorporated herein by reference. As described therein, registration inspection of a composite article undergoing fabrication is accomplished by producing an image of the article and then analyzing the image to detect the position of one or more components. The detected positions are then compared to ideal positions to thereby determine whether the one or more components are properly positioned. This registration inspection system employs conventional video cameras for capturing visible and ultraviolet light reflected by and/or transmitted through components in order to produce still video images of such components. Thus, after producing a video image of a composite article and its several components, the image can be analyzed to determine whether the components are properly positioned and registered with one another.
Although highly useful for many applications, the inventors hereof have determined that the inspection system disclosed in the aforementioned patent, and similar systems, have certain shortcomings. For example, such systems are not well suited for determining the presence and/or positions of components underlying other components which are substantially opaque to visible and/or ultraviolet light. Additionally, such systems are not well suited to determining the presence and/or positions of components which tend to scatter visible and ultraviolet light.
Another exemplary inspection system, disclosed in U.S. Pat. No. 6,224,699, employs infrared detectors for producing infrared images of products undergoing formation by sensing infrared radiation emitted by heated product components. The produced images are then compared with reference information to determine, for example, whether the product components are properly positioned. However, this system is not well suited to detecting product components which have cooled, or which were never heated in the first instance.
The inventors hereof have also recognized that prior art inspection systems and processes are not well suited to detecting the distribution and/or concentration level (e.g., quantity) of certain product components.